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February 27 2019. A report appearing in a recent issue of the Journal of Alzheimer’s Disease documented the finding of researchers in Kanazawa, Japan of an association between higher blood levels of vitamin C and a reduced risk of cognitive decline in women with one or two copies of the gene APOE4, which is associated with a significant increase in the risk of developing Alzheimer’s disease.

The study included 349 participants in the Nakajima Study, a population-based longitudinal study that sought to investigate cognitive decline in older Japanese men and women. Cognitive status was evaluated and questionnaires concerning sociodemographic data, medical history and other factors were completed between 2007 and 2008 and at follow-up during 2014—2016.

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Seventy-two subjects were identified as carriers of the APOE4 gene. Among women with at least one copy of APOE4, those whose blood vitamin C levels were among the highest third had a 90% lower risk of cognitive decline (defined as mild cognitive impairment or dementia) at follow-up in comparison with women whose levels were among the lowest. In men who did not have the APOE4 variant, the risk of cognitive decline was 81% lower for those whose vitamin E levels were highest.

“Our results demonstrate the protective effects of vitamin C against dementia or cognitive decline in APOE4 carrier women,” Moeko Noguchi-Shinohara and colleagues write. “The powerful antioxidant function of vitamin C might be stronger in APOE4 carriers, because they have more subclinical amyloid beta deposition in the brain compared with non-E4 carriers.”

“Randomized controlled trials evaluating antioxidants for the reduction of cognitive decline are necessary with selected participants with low blood vitamin C and E concentrations, stratified by gender and APOE4,” they conclude.